A new high-frequency audiometer has been developed with NIH/NINCDS support. The audiometer uses digital signal processing to calibrate each ear tested, and is able to provide accurate estimates of actual sound pressure at the apex of the auditory canal. The new audiometer can serve in the establishment of valid audiometric standards for the normal population, and for accurate determination of high-frequency hearing loss, an early warning of long-term effects of ototoxic drugs or noise exposure. The primary new technique used is calibration by spectral analysis of an impulse reflected from the ear canal. The applicants will transform the present laboratory instrument into a product that is compact and as low in cost as possible. Such a product would be responsive to expressed needs of audiological clinics. Product development will include simplification of construction, provision of a small, inexpensive built-in microcomputer, and additional software taking operator human factors into account. Initial research will be concerned with the effects of operator errors on estimates of sound pressure; optimum information feedback rates to minimize operator error in fitting the audiometer coupling to the subject's ear; and numerical precision required in the audiometer calibration algorithm. Later work will include study of the incorporation of tympanometry in the same instrument; automatic preparation and printing of audiograms; versions for use with external microcomputers.